/*
 * @lc app=leetcode.cn id=70 lang=cpp
 *
 * [70] 爬楼梯
 */

// @lc code=start
class Solution {
public:
    /*
    int climbStairs(int n) {
        if(n == 0 || n == 1 || n == 2)
            return n;
        vector<int> dp(n + 1,0);
        dp[1] = 1;
        dp[2] = 2;
        for(int i = 3;i <= n;i++)
        {
            dp[i] = dp[i - 1] + dp[i - 2];
        }
        return dp[n];
    }
    */
    int climbStairs(int n) {
        if(n == 0 || n == 1 || n == 2)
            return n;
        int a = 1;
        int b = 2;
        int temp = 0;
        for(int i = 3;i <= n;i++)
        {
            temp = a + b;
            a = b;
            b = temp;
        }
        return temp;
    }
};
// @lc code=end

